Plunger pump



July 21, 1936. E. JLsvENsoN 2,048,524

PLUNGER PUMP Filed July 5, 1931 3 Sheets-Sheet l 1 Ernest J'Suenson y936. Bis/E1450 2,048,524

PLUNGER PUMP i d July 5, 1931 s Sheets- She et 2" u y '21, 1936- E. J.SVENS.OIN 48 4 N PLUNGER PUMP :Filed July 5, 1951 3 Sheets-Sheet-SPisi-qu ms'pulcsnzu'rflNGuunR. DISPLRCEMENT Patented July 21, 1936PLUNGER PUMP Ernest J. Svenson, Rockford, 11]. Application July 3,1931,. Serial No. 548,569

11 Claims. My invention relates generally to plunger pumps andparticularly to plunger pumps adapted to be driven at relatively highspeeds.

In certain types of plunger pumps fluid under relatively low pressure isdirected froma control valve to one end of a piston chamber during theintake stroke of the piston within said chamber, and said fluid is thensubjected to pressure within the chamber during the compressing strokeoi the piston and is forced in a reverse direction through said valve.In other words, a volume of low pressure fluid is directed through apassageway in a given direction, and this same fluid, after beingsubjected to .an increase in pressure, must be suddenly urged in areverse direction through said passageway. Therefore, it is verydesirable to have the valve which controls the intake and discharge ofthe low and high pressure fluids accurately timed so as to enable thepump mechanism to be driven at a relatively high speed withoutexperiencing difflculties which might arise as a result of the suddenreversal in direction of flow of thelow and high pressure fluids. If thevalve which controls the flow of fluid toward and away from the pistonsor plungers of the pump is timed and operated so as to suddenly cut ofl?communication between the piston chamber and the high pressure side ofthe circuit and contemporaneously open said chamber to the low pressureor intake side of the circuit during the interval when the pistonremains stationary at the end of its stroke, I have found that the pumpmay be efliciently operated at very high speeds. Heretofore it has beenfound necessary to employ check valves and other pressure relievingdevices in combination with high. speed plunger pumps in order toovercome difliculties which otherwise result from the frequent,successive changes from low to high pressure fluid conditions, or viceversa, Employing these auxiliary pressure relieving devices not onlycomplicates the meehanical structure of the pump, but also introduceselements which areconstantly subjected to wear, and hence must berepaired or replaced at frequent intervals in order to maintain the pumpin running order. x

a It is one of the primary objects of my present invention to overcomethe above mentioned difflculiies by providing a plunger pump equippedwith valve mechanisms whichare operated in timed relation with respectto the reciprocation oi" the pump pistons in such a manner that theopening and closing of said valves with respect to the low and highpressure fluids will take place during the interval when the pump pistoncompanion to each valve mechanism is substantially motionless. I 4

A further object of my invention is to provide a fluid pump of thereciprocable plunger type, which is adapted to receive fluid under arelatively low pressure, and discharge said fluid under a relativelyhigh pressure through the agency of an improved valve mechanism whilesaid pump is operating at a relatively high speed.

More specific-ally, my invention contemplates the provision, incombination with a plunger pump of the type having a plurality of radialpistons actuated by a centrally disposed eccentric mechanism, of aplurality of valves, each valve being companion to one of the pistonsand adapted to control the flow of low pressure fluid thereto and thehigh pressure fluid therefrom, the functioning of each valve being timedso as to eifect the sudden shifting from low to high fluid pressureconditions in the companion piston chamber, or vice versa, when theeccentric piston actuating mechanism is substantially on dead centerwith respect to the companion piston, that is, when the piston companionto the valve is substantially motionless.

Still morespecifically, my invention contemplates the provision, withthe combination of elements recited above, of a plurality ofreciprocable control valves, each of which is companion to one of thepiston chambers and an improved eccentric driving mechanism for saidvalves, which is angularly disposed with respect to the eccentricdriving mechanism for the pistons in such a manner as to properlycontrol, the interval during which each valve functions to eflfect theshifting between low and high pressure fluid conditions within thepiston chamben.

A further object of my invention is to provide means in combination withthe pump pistons and eccentric driving means therefor for causing saidpistons to experience acceleration which is symmetrical with thedeceleration during at least the compression stroke thereof, and to thisend I propose to provide shiftable members having surfaces shaped anddisposed so as to cause the pistons to experience the above mentionedsym-- companion. to each pump piston with respect to an eccentricdriving means as to make a rolling, driving contact with the pistons forthe purpose set forth above, and .for'transmitting a driving.

companion thereto, whereby to maintain the pisg tons in a. balancedcondition free from laterally acting forces. l I

The foregoing and numerous other objects and advantages will be moreapparent from the following detail description when considered inconnection with the accompanying drawings, where- Figure l is a centralsectional view taken longitudinally of a pump mechanism embodying myinvention, said view being taken substantially along the line I-l ofFigure 2;

- Figure 2 is a transverse sectional view of said pump takensubstantially along the line 2-2 of Figure 1;

Figure 3 is also a transverse sectional view thereof taken substantiallyalong the line 33 of Figure 1;

Figure 4 is an enlarged fragmentary view of one of the valves disclosingthe position thereof just as it cuts off communication between thepiston chamber and the high pressure side of the pump;

Figure 5 is a similar view disclosing the position occupied by the valvejust as it is about to establish communication between the pistonchamber and the low pressure or intake side of the pump;

Figure 6 diagrammatically discloses one of the positions occupied by theeccentric piston driving mechanism when the valve member'companion tosaid piston suddenly functions to cut off the piston chamber from thehigh pressure fluid and establish communication with the low pressurefluid;

Figure 7 illustrates various positions occupied by each finger as itswings from the low to the high position during 180 rotation of theeccentric driving member;

Figure 8 is a fragmentary disclosure of one of the fingers to moreclearly illustrate the curvatures of the oppositely disposed surfaces ofthe free extremities of the fingers; and

Figure 9 is a graphic representation of the symmetry in pistondisplacement during the first and second half of the compressive strokethereof.

Referring now to the drawings more in detail wherein like numerals havebeen employed to designate similar parts throughout the various figures,it will be seen that one embodiment of my invention contemplates aplunger pump which includes a stationary cylinder block or support iii,an intermediate casing l2 secured to the block ID by bolts l4, and anend casing section l6 which is secured to the intermediate casing l2 bybolts or screws 18. The support or block In is provided with a pluralityof radial piston chambers 20, which house companion pistons or plungers22. The outer ends of the chambers 20 are closed by means of threadedcaps 24, and each chamber-20 communicates at its outer end with a valvemechanism 26 through a passageway 28.

Each valve mechanism 26 includes a cylindrical valve member 30 which isreciprocable within a radial valve chamber 32 formed within the supportor block In. The valve member 30 comprises an end cylindrical section30a an oppositely disposed end section 3017, and a central reducedsection 300. The central or reduced section 30c presents an annularvalve chamber or port 34, which is in continuous communication with thepassageway 28."

Low pressure fluid for charging the piston chambers 20 is adapted tobeintroduced from a source of supply (not shown) through a pipe line 36,which is in constant communication with an an external source of supply(not shown).

2,048,524 load to a localized central portion of the piston outerannular passage 38 and an inner annular passage 46 formed within theintermediate casing section i2. The annular passageway 38 communicateswith the outer end of each valve chamber 32 through a port 42, and theannular pas- 5 sageway 40 communicates with the'other end of said valvechamber through a port 44. A third annular passageway 46 communicateswith the central portion of the valve chamber 32 through a port 48. Thisannular passageway is adapted to communicate with a point externally ofthe pump, as, for example, with the high pressure side of a hydraulicactuator (not shown) through a pipe line 50. Fluid within the annularpassageways 38 and 4B is under arelatively low pressure, while fiuidwithin the passageway 46 is under a relatively high pressure. Themechanism for imparting movement to the pistons or plungers 22 includesa plurality of pivoted fingers 52 which are arranged tangentially withrespect to and 20 rest upon the peripheral surface *of an anti-frictiondriving ring 54. The driving ring 54' -mounted upon the cylindricalsection of a driving" member 56, which is adapted to be eccentricallypositioned with respect to a driving sleeve 58. 25 The pistons 22 andthe valve members 30 radiate. from a horizontal axis which is coincidentwith the axis of the sleeve 58, The driving member 56 is formed with asection 69, which is slidable transversely of the sleeve 58 within aslot 62, Figures 1 and 2. The sleeve 58 is mounted with in suitableanti-friction bearings 64 and 66, the bearing being mounted within theend casing section l6 and the bearing 66 within the block or section ID,as clearly shown in Figure 1. The sleeve 58 is driven by an annular gear68 which is coupled to the sleeve by means of a depressible key 10. Thegear 68 is adapted to be driven from The driving member 56 is adapted tobe laterally adjusted within the sleeve 58 through the agency of anadjusting member 12, which is formed with an intermediate cylindricalsection 12a mounted within the sleeve 58 andan angu= larlydisposedprojection 12b which extends within a companion angularlydisposed recess provided within the driving member 56. By applying aturning member, such as a wrench, to a nut 14, movement longitudinallyof the sleeve 58' is imparted to the adjusting member 12. 55

To more clearly illustrate the symmetrical manner in which the fingers52 function to accelerate and decelerate the plungers during thecompression stroke thereof. I have included Figures 7, 8; and 9. Figure7 illustrates various positions "cc-'- cupied by each finger as theeccentric driving member 54 travels through beginning with the finger inits lower position and continuing by eight successive equal movements ofthe driving member until the finger reaches its upper position. no Thecenter about which the driving member 54 rotates is designated by theletter A. The center-of the driving member 54 is designated by theletter B, beginning at the lower point with B and termi natin'g at theupper position with B Thus a8 33 the center B moves from the-point B toB, it will have experienced one-eighth of the first 180 of movement, andthe piston will have traveledthe distance U, as shown in Figure '7.Thusduring the next one-eighth movement of the center B, 7 namely from Bto B, the piston will shift through the distance D. In the same manner,the distance B -B corresponds with the distance 5, etc. Particularattention is directed to the diswhich are equal. In other words, thereis symmetry in relationship between the distances on opposite sides ofthesolid line in Figure '1, which indicates the position occupied by the-piston 22 when it has completed half of. its stroke. Stating it inanother way,.the increase in rate of displacement of each piston orplunger 22 during the first half of its compression stroke issymmetrical with the rate of displacement during the second half of thecompression stroke. With the view of still more clearly illustrating thesymmetry in piston movement, I have disclosed in Figure 9, a graph orchart in which I have plotted the angular displacement of the drivingmember 54 against the displacement of the piston. The points have beengiven letterv designations corresponding with letter B to B inclusive inFigure '7. From Figure 9, the symmetrical functioning during the firstand second half of the piston stroke will be more apparent. Thismovement should be distinguished from the conventional piston andconnecting rod, wherein the displacement of the piston during one-halfof the .crank shaft rotation is not equal to the displacement during thesecond half of the crank shaft rotation.

The structural arrangement of the finger 52 is such as to cause theuniformity or symmetry in movement as mentioned above. To more clearlydisclose the various positions occupied by the fin- Eers 52, the piston22, and the driving member or ring 54, I have shown correspondingpositions, corresponding lines, such as dotted lines, dot and dashlines, etc.

Attention is directed to the fact that the fingers 52 are provided withoppositely disposed arcuate surfaces 52a and 52b which are so arrangedas to impart symmetrical motion to the pistons 22 in response to themovement of the eccentric driving ring 54 through its orbit. By havingthis motion, the pistons accelerate and decelerate at the same rate, andas a result a uniform fiow of fluid under pressure from the chambers 20is obtained.

Outward movement is imparted to the valve members 30. by a ring orannulus it, which encircles and is mounted upon an eccentric member 78.This member 78 is in turn keyed to the sleeve member 58, as clearlyshownin Figure 2. The mounting of the ring 16 is such that thefrictional engagement of the valve members 3!! therewith is normallysuilicient to prevent rotation of the member 18 during the rotation ofthe eccentric I8. Thus, by providing the ring 18, no side thrust isimparted to the valve members 30 during the actuation of the eccentric18. If in certain instances it may be found necessary to further preventrotation of the ring 12, this may be done by merely welding or otherwiseforming a projection 80 on the peripheral surface thereof, as indicatedby the dot-and-dash lines in Figure 2. This would of course necessitatethe provision of a recess 800 within the block i0.

From the foregoing it will be apparent that as the driving ring 54 isswept through its orbit in response to the rotation of the eccentricallypositioned driving member 56, the pistons or plungers 22 will besuccessively urged outwardly to compress fluid present within the pistonchambers 20. The inward movement of the pistons 22 is occasioned inresponse to the introduction of fluid under relatively low pressure, andit is the functioning of the valve member 30 in connection withcontrolling the low and high pressure fluids which forms an importantfeature of my present invention. In this connection attention isdirected to the fact that the eccentric valve driving ring 18 issubstantially ninety degrees out of phase with the plunger driving ring54. This can best be observed by referring to Figure 3. The fixed axisabout which the pistons 22 and valve members 30 are radially disposed isindicated by the letter A, while the axis of the driving member 56 andring 54 is indicated by the letter B, and the axis of the eccentricdriving ring 16 is indicated by the letter C. These notations areuniform through the various figures. In Figure 3 it will be noted thatthe axis B of the ring 54 is ninety degrees out of phase with the axis Cof the ring I6, the ring 16- being shown' by dot-and-dash lines inFigure 3. Bearing the phased relationship of these driving rings inmind, it will be seen that, when the driving ring 54 occupies its deadcenter with respect to the piston which I have designated by the letterD, said piston will, during a fractional moment, be substantiallymotionless. In fact, when the high point of the ring 54 is positioned ondead center. as shown in Figure 3, or within two degrees of either sidethereof, substantially no movement is imparted to the piston 22. I havedetermined that the degree of movement experienced by the piston Dwithin this four-degree range of angular movement of the driving ringwith a one-half inch stroke, is substantially .00012 inch. Referring nowto the valve member which is companion to the piston designated by theletter D, it will be seen that this valve member, which I havedesignated by the letter D, Figures 1 and 2, is experiencing its maximumspeed of travel, while the piston D is substantially stationary ormotionless. It will also be apparent that the valve member D is not onlyexperiencing its maximum movement at this time, but is also closing theport 48 and opening the port 44. In other words, at the time the pistonD is inactive, that is to say, at the time the fluid within thecompanion passageway 2B is motionless, the valve member D is positionedas shown in Figure 4. The valve member D in this position has justclosed the port 48. The valve member will continue to move inwardly adistance of .018 inch to the position designated in Figure 5, in whichposition it is about to open communication between the port 44 and theannular passage or port 34. During this .018 inch movement of the valvethe companion piston D has only traveled a distance of .00012 inch. Thusduring the four-degree travel of the driving ring 54, as clearlyindicated in Figure 6, the piston D experiences practically no movement,while the companion valve member moves at its maximum speed a sufficientdistance to close the high pressure port 48 and open the low pressure orintake port 44. The piston designated by the letter D and the companionvalve designated by the letter D have been selected merely to illustratethe functioning of all of the pistons and valve members. Thus it will beapparent that when each of the plungers or pistons 22 omupies itssubstantially motionless position, the valve companion thereto isexperiencing its maximum speed of travel and is closing one port andopening another.

Thus far I have described the timed relationship bc-tween the valvemembers and their companion pistons in connection with the change fromhighpressure to low pressure fluid conditions. It will be obvious thatthe same timed relationship holds true when the valve members operate tochange from low pressure to high pressure conditions. In otherwords,'when the valve member moves outwardly so as to close the port 44,as shown in Figure 5, and subsequently open the high pressure port 48 soas to enable fluid under pressure to be discharged from the companionpiston chamber 20, the piston within said chamber will be initiating itscompressing stroke.

In the operation of my improved pump or motor mechanism rotation isimparted to the sleeve 58 and its associated driving member 56 throughthe agency of the gear 68, and this rotation causes the driving ring .54to successively move the pistons 22 outwardly, and causes the drivingring 16 to successively move the valve members 30 outwardly. A portionof the fluid underzrelatively low pressure from the pipe line 36 entersthe outer ends of the valve chambers 32 so as to constantly urge thevalve members into engagement with the peripheral surface of the drivinring 16 and the remaining portion of said fluid is directed into theport 44. Assuming that the valve designated by the letter D is justreaching the position shown in Figure 4, it will be clear thatcommunication between the passageway 28 and the high pressure dischargeport 48 is being closed, and at this moment the piston D has reached theouter limit of its stroke and is substantially motionless. In fact,during a twodegree angular displacement of the driving ring 54 on eitherside of the dead center line shown in Figure 6, the piston D experiencessubstantially no movement. During this four-degree displacement thevalve member D is experiencing its maximum movement and shifts from theposition shown in Figure 4 to the position shown in Figure 5. In Figure5 the port is sealed or. closed; while the port 44 is about tobeopened:When the port 44 opens the piston D will begin its inward stroke and isin readiness to receive fluid under low pressure from the port 44. Uponreaching the limit of its inward stroke, the piston D again.

experiences substantially no movement, and during this interval thevalve member D serves to close the port 44 and open the port 48 so thatas. the piston begins its outward stroke, fluid under pressure will passfrom the piston chamber 20 through the passageway 28, the valve passageor port 44, the port 48, and thence through the an- From the foregoingdescription it will be understood that each of the valve members 30functions to change from high pressure to low pressure conditions, orvice versa, during the interval when the piston companion thereto issubstantially motionless. This means that the fluid body within thepassageway 28 companion to said valve and piston, is also substantiallymotionless, and is therefore in readiness to be moved in eitherdirectionwithout experiencing the slightest degree of pulsation. Should thechange from low to high pressure conditions, or vice versa, be made at atime when the fluid within the passageways 28 and pistgn chambers 20companion thereto is being moved in either direction, these pulsatingand other disturbing effects would be experienced with the result thatthe pump could not be operated at its maximum efficiency nor at anyappreciable speed. By having the eccentric for controlling thefunctioning of the valve members and the eccentric for actuating thepistons driven -by the same mechanism, I am able to materially radialvalve arrangement, the high pressure fluid simplify the pumpconstruction and to obtain accurate timed relation between thefunctioning of the companion valves and pistons. It will be seen thatthe valve members 30 are continually urged inwardly through the actionof the low pressure 5 fluid from the pipe line 36, which enters theouter ends of the valve chambers 32 through the annular passagway 38 andthe ports 42 communicating therewith. By employing my simplifled 10 atno time communicates with the low pressure 'fluid, or vice versa, andthis is a condition which materially expedites the functioning ofthe'pump. Obviously my improved valve construction and mechanismassociated therewith are not limited 15 for use in connection withpumps, but are adapted for use in various types of fluid motors whereinit is desirable to maintain the low pressure and high pressure fluidsoperable independently of each other, and where a change from one pres-0 sure condition to another is to be made when the fluid within themotor or pump is substantially inactive or motionless.

From the foregoing description it will also apparent that the freeextremities of the pivoted fingers are shaped and disposed with respectto the eccentric-driving. means so as to effect a roll-' ing, drivingcontact therewith, and further, to transmit a driving load to alocalized central portion -of a' companion piston in the direction in 30which the piston moves. In other words, the pivoted fingers, in additionto causing the pistons to experience symmetrical acceleration anddeceleration during at least'the compression stroke thereof, also serveto preclude the transmission of 35 load to said pistons which would havea tendency to cook the piston and thereby subject the piston to unevenwear. Thus it might be said that my improved finger construction servesto maintain the pistons in balance, as distinguished from drivn ingmechanisms wherein the force which serves to shift the piston does notact continuously in the direction of movement of the piston, and in amanner to preclude the tendency for the piston to tilt or cock withinits cylinder. My fingers are 5 so shaped and disposed as to continuouslyapply the driving forceat a central localized area at the inner ends ofthe pistons, thereby maintaining the piston in balance", that is to say,free from any forces tending to shift the piston laterally.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A pump including a piston support, a plurality of radiallyreciprocable pistons in said 55 support, rotary driving meansoperatively associated with said pistons, and a pivoted fingerassociated with each piston and having a surface engaging the piston andan oppositely disposed surface engaging the periphery of the rotary 60driving means, at least one of said surfaces being curved, the shape anddisposition of said surable means adapted to engage the inner end of acompanion piston, and a surface having a difierent curvature adapted toengage the periphery of said rotary driving means, said surfaces beingshaped and disposed with respect to said pistons and rotary drivingmeans for causing the piston companion thereto to experienceacceleration which is symmetrical with the deceleration during thecompression stroke thereof.

3. A plunger pump of the class described including a cylinder block, aplurality of radially disposed pistons reciprocable within said block, adriving mechanism for actuating said pistons, said mechanism causingrelative dwells of the pistons at the ends of the movement thereof, aplurality of valves; one companion to each piston, a passagewayconnecting each of said valves with its companion piston, intake anddischarge ports adapted t'o'be opened and closed by said valves, eachvalve in one shifted position being adapted to direct fluid from theintake port through said passageway to said piston and in anothershifted position adapted to receive fluid under pressure from saidpassageway and direct said fluid to the discharge port, each valvearranged to overlap companion intake and discharge ports during therelative dwells otthe piston communicating therewith, means foractuating each valve to close one of said ports and open the otherduring the dwell of the companion piston, whereby to enable the pump tobe efiiciently driven at relatively high speeds, and shiftable meansinterposed between said driving mechanism and pistons and supportedindependently thereof, said shiftable means being shaped and disposedwith respect to both said driving mechanism and the inner ends of saidpistons so as to cause said pistons to experience movement during thefirst half 01' the compression stroke which is symmetrical with themovement during the second half of the compression stroke.

4. A plunger pump of the class described including a cylinder block, aplurality of radially disposed pistons reciprocable within said block, adriving mechanism for actuating said pistons,

.said mechanism causing relative dwells oi the pistons at the ends ofthe movement thereof, a plurality of valves, one companion to eachpiston, a passageway connecting each of said valves with its companionpiston, intake and discharge ports adapted to be opened and closed bysaid valves, each valve in one shifted position being adapted to directfluid from the intake port through said passageway to said piston and inanother shifted position adapted to receive fluid under pressure fromsaid passageway and direct said fluid to the discharge port, each valvearranged to overlap companion intake and discharge ports during therelative dwells of the piston communicating therewith, rotary drivingmechanism including a member rotatable about a fixed axis, a drivingmember eccentrically adjustable with respect to and driven by saiddriving member for imparting movement to said pistons, a secondeccentric driving means carried by the first mentioned driving memberfor actuating each valve to close one of said ports and open the otherwhen the fluid within the companion passageway. is substantiallymotionless, and shiitable means interposed between said drivingmechanism and-pis- :ons and supported independently thereof, said:hiitable means being shaped and disposed with aspect to said drivingmechanism and the inner :nds of said pistons so as to cause said pistonsto experience movement during the first half of the compression strokewhich is symmetrical with the movement during the second half of thecompression stroke.

5. A plunger pump of the class described including a cylinder block,- aplurality of radially disposed pistons reciprocable within said block, adriving mechanism for actuating said pistons, said mechanism causingrelative dwells oi the pistons at the ends of the movement thereof, aplurality of valves, one companion to each piston, a passagewayconnecting each of said valves with its companion piston, intake anddischarge ports adapted to be opened and closed by said valves, eachvalve in one shifted position being adapted to direct fluid from theintake port through said passageway to said piston and in anothershifted position adapted to receive fluid under pressure from saidpassageway and direct said fluid to the discharge port, eccentricdriving means for actuating each valve, each valve being adapted tooverlap said ports as the companion piston reaches the limit of itscompression stroke, thereby enabling one port to close before openingthe other por't, said valve actuating means functioning to open andclose said ports through the agency of the valve when the companionpiston is positioned at one extremity of its stroke and the valve isexperiencing its maximum speed of travel, and shiftable means interposedbetween said driving mechanism and pistons and supported independentlythereof, said shiftable means being'shaped and disposed with respect tosaid driving mechanism and the inner ends of said pistons so as to causesaid pistons to experience movement during the first half of thecompression stroke which is symmetrical with the movement during thesecond half of the compression stroke.

6. A plunger pump of the'class described including a cylinder block, aplurality oi radially disposed pistons reciprocablewithin said block, adriving mechanism for actuating said pistons including an eccentricdriving member and a shiftable member having oppositely disposed arcuatesurfaces interposed between said driving member and each piston andsupported independently thereof, said shiftable member. being shaped anddisposed with respect to both the periphery of said driving member andthe inner ends of said pistons so as to cause said pistons to experiencesymmetry in acceleration and deceleration during the outward movementthereof and cooperating with the-eccentric driving member in causing arelative dwell of the pistons upon the completion of the compressionstroke thereof, a plurality of valves, one companion to each piston, apassageway connecting each of said valves with its companion piston,intake and discharge ports adapted to be opened and closed by saidvalves, each valve in one shifted position being adapted to direct fluidfrom the intake port through said passageway to said piston and inanother shifted position adapted to receive fluid under pressure fromsaid passageway and direct said fluid to the discharge port, and meansfor actuating each valve to close one'oi' said ports and open the otherduring the above mentioned dwell of the companion piston, whereby toenable the pump to be emciently driven at relatively high speeds.

7. A plunger pump of the class described including a cylinder block, aplurality of radially disposed pistons reciprocable within said block, adriving mechanism for actuating said pistons including an eccentricdriving member and a pivotal finger interposed between said drivingmember and each piston, said finger being shaped and disposed withrespect to both the periphery of said driving member and the inner endsof said pistons so as to cause said pistons to experience symmetry inacceleration and deceleration during the outward movement thereof andcooperating with the eccentric driving member in causing a relativedwell of the pistons upon the completion of the compression-strokethereof, a plurality of valves, one companion to each piston, apassageway connecting each of said valves with its companion piston,intake and discharge ports adapted to be opened and closed by saidvalves, each valve in one shifted position being adapted to direct fluidfrom the intake port through said passageway to said pistons and inanother shifted position adapted to receive fluid under pressure fromsaid passageway and direct said fluid to the discharge port, andmeansfor actuating each valve to close one of said ports and open theother during the above mentioned dwell of the companion piston, wherebyto enable the pump to be efliciently driven at relatively high speeds.

8. A pump including a piston support, a plurality of radiallyreciprocable pistons in said support, rotary driving means operativelyassociated with one end of the pistons, and shiftable means interposedbetween the driven end of each piston and the periphery of said rotarydriving means, said shiftable means being shaped and disposed withrespect to both the pistons and the driving means so as to make arolling contact therewith for causing each piston to experienceacceleration whichissymmetrical with the deceleration during thecompression stroke thereof, and supporting means independent of saiddriving means for mounting said shiitable means within the p mp.

a, 9. A pump including a piston support, a pinrality oi. radiallyreciprocable pistons in said support, rotary driving means operativelyassociated with one end of the pistons, and shittable means interposedbetween the driven end of each piston and the periphery of said rotarydriving means, said shiftable means being shaped and disposed withrespect to said rotary driving means and 'said pistons for transmittinga driving load to a localized central portion of each piston in thedirection of movement of said piston and for causing each piston toexperience acceleration which is symmetrical with the decelerationduring the compression stroke,- and supportingmeans independent of saiddriving means for mounting said shiftable means within the pump.

10. A pump including a piston support, a plurality of radiallyreciprocable pistons in said supv port, rotary driving means operativelyassociated with said pistons, and shiftable means comprising a pivotedfinger interposed between the inner end of each piston and the peripheryof said rotary driving means, said finger being shaped and disposed withrespect to said rotary driving means and the inner ends of said pistonso as to cause each piston to experience acceleration which issymmetrical with. the deceleration during the compression strokethereof.

11. A pump including a piston support, a plurality oi radia lyreciprocable pistons in said support, eccentrically adjustable rotarydriving means operatively associated with said pistons, a pivoted fingerassociated with each piston and having asurface engaging the piston andan op- ERNEST J. SVENSON.

